Modeling and design of permanent magnet biased radial-axial magnetic bearing by extended circuit theory

Permanent magnet biased radial-axial hybrid magnetic bearing possesses complicated structure, which makes the design and analysis difficult. In this paper, the permeances of each part of the flux path including the leakage permeance are analyzed thoroughly by considering the geometry structure and the distribution of air gap flux. Then the relatively precise mathematical model of the hybrid magnetic bearing is deduced. Based on the mathematical models of the hybrid magnetic bearing, a prototype hybrid magnetic bearing is designed, and the calculation formulas of magnetic suspension forces, the force-displacement coefficients and the force-current coefficients are deduced. Finally, the design and analysis of the prototype hybrid magnetic bearing was verified by 3D electromagnetic finite element method.